UNIVERSITY  OF  CALIFORNIA  PUBLICATIONS. 


COLLEGE  OF  AGRICULTURE. 


AGRICULTURAL  EXPERIMENT  STATION. 


REPORT  OF  THE  PLANT  PATHOLOGIST 
TO  JULY  1,  1906 


By  RALPH    E.  SMITH. 


BULLETIN    No.     184 

(Berkeley,  Cal.,  January,  1907.) 


SACRAMENTO: 

w.  w.  shannon,       :         :  :         :       superintendent  state  printing. 

1907. 


BENJAMIN   IDE  WHEELER.  Ph.D.,  I,I,.DM  President  of  the  University, 


EXPERIMENT  STATION  STAFF. 

E.  J.  WICKSON,  M.A..  Acting  Director  and  Horticulturist. 

E.  W.  HILGARD.  Ph.D.,  LL.D.,   Chemist. 

W.  A.  SETCHELL.  Ph.D.,  Botanist. 

EL  WOOD  MEAD.  M.S.,  C.E.,  Irrigation  Engineer. 

C.  W.  WOODWORTH,  M.S.,  Entomologist. 

R.  H.  LOUGHRIDGE,  Ph.D.,  Agricultural  Geologist  and  Soil  Physicist.     (Soils  and  Alkali.) 

M.  E.  JAFFA.  M.S.,  Chemist.    (Eoods,  Nutrition.) 

G.  W.  SHAW,  M.A.,  Ph.D.,  Chemist.     (Cereals,  Oils,  Beet-Sugar.) 

GEORGE  E.  COLBY,  M.S.,  Chemist.     (Fruits,  Waters,  Insecticides.)     [Absent  on  leave.] 

RALPH  E.  SMITH,  B.S.,  Plant  Pathologist. 

A.  R.  WARD,  B.S.A.,  D.V.M.,  Veterinarian  and  Bacteriologist. 

E.  W.  MAJOR,  B.Agr.,  Animal  Industry. 

F.  T.  BIOLETTI,  M.S.,  Viticultunst.     (Grapes,  Wine,  andZymology.) 
H.  M.  HALL,  M.S.,  Assistant  Botanist. 

H.  J.  OUAYLE,  A.B.,  Assistant  Entomologist. 

JOHN  S.  BURD,  B.S.,  Chemist,  in  charge  of  Fertilizer  Control. 

C.  M.  HARING,  D.Y.M.,  Assistant  Veterinarian  and  Bacteriologist. 
H.  J.  RAMSEY, 

T.F.HUNT,  (.       Assistant  Plant  Pathologists. 

E.  H.  SMITH,  M.S.,    ) 

R.  E.  MANSELL,  Assistant  in  Horticulture  in  charge  of  Central  Station  Grounds. 

G.  R.  STEWART,  B.S.,  Assistant  in  Station  Laboratory. 
,  Assistant  in  Soil  Laboratory. 

RALPH  BENTON,  B.S.,  Assistant  in  Entomology. 

LUDWIG  ROSENSTEIN,  Laboratory  Assistant  in  Fertilizer  Control. 

ALFRED  TOURNIER,  Assistant  in    Viticulture. 

HANS  HOLM,  Student  Assistant  in  Zymology. 

A.  J.  GAUMITZ,  M.S.,  Assistant  in  Cereal  Laboratory. 

J.  C.  BRADLEY,  A.B.,  Assistant  in  Entomology. 

D.  L.  BUNNELL.  Clerk  to  the  Director . 


JOHN   TUOHY,  Patron, 

Tulare  Substation.   1  ulare. 


J.  T.  BEARSS,  Foreman, 

J.  W.  MILLS,  Horticultural  Assistant  in  Southern  California,  Riverside. 

J.  V7.  ROPZR,  Patron,  )  . 

>      Lmversity  Forestry  Station,  Chico. 
K.  C.  MILLER  In  charge,         ) 

\ ONES,  Patron,  >     _    .  .    _,        .      e.   ..        e      .     __      . 

University  Forestry  Station,  Santa  Monica. 


rNGHAM,  Foreman, 

•"f  J.  HUNTLEY,  Foreman  of  California  Poultry  Experiment  Station,  Petaluraa. 

The  Station  publications  (Reports  and  Bulletins),  so  long  as  avail- 
able, will  be  sent  to  any  citizen  of  the  State  on  application. 


REPORT  Of  THE  PLANT  PATHOLOGIST. 

By  RALPH  E.  SMITH. 


General  Review. — The  present  report  of  this  Division  covers  a  period 
which  has  been  characterized  by  very  greatly  increased  activity  and 
volume  of  work,  due  to  the  appropriation  by  the  last  Legislature  of 
funds  for  a  number  of  special  undertakings  and  investigations  in  plant 
pathology,  the  financial  promotion  of  several  special  investigations  by 
private  concerns,  and  in  general  to  the  increased  public  interest  in 
the  work  of  this,  as  of  other  departments  of  the  Experiment  Station. 
These  factors  have  contributed  very  materially  to  the  growth  of  the 
Division  since  its  establishment  in  1903.  Beginning  at  that  time  with 
the  unaided  services  of  the  writer,  and  with  practically  no  equipment  or 
facilities  for  work,  the  past  season  has  seen  twelve  or  more  assistants 
engaged  in  active  field  and  laboratory  work  in  the  various  investigations 
undertaken,  a  laboratory  and  office  maintained  at  the  University,  a 
temporary  laboratory  in  use  in  southern  California,  provision  made 
for  a  permanent  laboratory  in  the  same  region,  and  much  work  of 
value  completed  or  begun. 

Plant  pathology,  looked  upon  either  as  a  science  or  from  the  stand- 
point of  its  economic  value,  has  nowhere  so  great  a  field  as  in  Cali- 
fornia. The  extensive,  specialized  development  of  agriculture  and 
horticulture,  the  great  abundance  of  plant  troubles  and  the  very 
slight  extent  to  which  they  have  been  studied,  and  the  appreciative 
attitude  of  the  public,  afford  the  greatest  stimulus  to  the  professional 
investigator;  while  for  the  student  of  plant  pathology  the  field  and 
opportunities  for  study  and  research  are  unbounded  and  the  conditions 
most  favorable.  The  greatest  need  in  the  State  at  present,  as  regards 
plant  diseases,  is  that  of  investigation.  Not  only  are  many  of  our 
most  serious  troubles  peculiar  to  this  region  and  their  intimate  nature 
wholly  or  largely  unknown,  but  even  in  the  case  of  plant  diseases 
common  to  other  sections,  experience  is  continually  showing  that  facts 
and  methods  of  established  value  do  not  entirely  apply  here.  The  very 
artificial  or  unnatural  conditions  under  which  a  large  part  of  our 
cultivated  vegetation  is  grown,  produces  unlimited  and  most  diverse 
vagaries  in  the  behavior  of  the  plants  themselves  and  in  the  con- 
ditions  and   agencies   which   affect   them.      Under  such   conditions   it 


--V  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION. 

seemed  more  and  more  evident  to  the  writer  that  both  the  demand 
and  the  opportunity  are  greatest  for  a  strong  department  of  investi- 
gation in  this  branch  of  the  Experiment  Station  work,  rather  than 
simply  a  bureau  of  information  or  pedantic  teaching,  and  it  is  his 
purpose  to  develop  this  Division  along  such  lines. 

The  work  of  the  Division  since  the  last  report  has  consisted  mostly 
of  several  special  investigations  or  undertakings  of  considerable 
importance,  many  miscellaneous  examinations  or  minor  studies,  a  very 
large  amount  of  traveling  and  personal  inspection  on  the  part  of  the 
writer  and  his  assistants,  the  preparation  of  three  bulletins  and  a 
number  of  contributions  to  the  horticultural  and  botanical  press,  and 
the  handling  of  a  rapidly  increasing  correspondence. 

The  main  lines  of  work  have  been : 

1.  The  Pear  Blight  investigation,  founded  on  an  appropriation  by 
the  last  Legislature. 

2.  The  Walnut  Blight  investigation,  also  provided  for  by  special 
funds  from  the  State. 

3.  The  Lemon  Rot  investigation,  supported  by  a  contribution  from 
the  lemon  interests  of  southern  California. 

4.  The  Beet  Blight  investigation,  carried  on  under  a  fund  guaranteed 
by  the  Spreckels  Sugar  Company,  and  contributed  to  by  the  other 
beet  sugar  manufacturers  of  the  State. 

5.  Peach  Blight  and  "Shot-hole  Fungus"  investigation,  begun  in  a 
small  way  in  1905  and  1906,  with  more  extensive  work  planned  for  the 
immediate  future. 

6.  Tomato  Disease  investigation,  begun  in  1905  and  still  continuing. 

7.  Asparagus  Rust  investigation,  begun  in  1903  and  practically 
completed  in  1905,  but  still  lacking  in  some  practical  details. 
Selection  and  propagation  of  rust-resistant  varieties  are  also  still 
going  on. 

8.  Rose  Disease  investigation,  concluded  and  ready  for  publication. 

9.  Citrus  Disease  investigation,  just  beginning. 

Besides  these  special  undertakings,  the  usual  correspondence  and 
course  of  the  work  have  brought  out  a  great  variety  of  matters  of 
interest  regarding  plant  diseases,  which  have  received  more  or  less 
attention.  Some  of  the  features  of  interest  of  this  sort  are  indicated 
in  the  article  on  plant  diseases  in  this  State,  found  elsewhere  in  this 
report.  It  may  also  be  said  that  in  this  general  way  conditions  are 
gradually  shaping  themselves  for  the  commencement  of  other  special 
investigations  of  a  number  of  serious  plant  diseases  concerning  which 
are  at  present  very  much  in  the  dark.  With  fully  equipped  labora- 
,  tories  and  permanenl  assistants  both  at  Berkeley  and  in  southern 
California,  the  Division  is  getting  more  and  more  into  shape  to  handle 
a  Large  amount  of  diversified  work. 


REPORT  OF  PLANT  PATHOLOGIST.  221 

The  publications  issued  from  this  Division  since  the  last  report 
include  Bulletin  No.  165,  Asparagus  and  Asparagus  Rust  in  California; 
Bulletin  No.  172,  Further  Experience  in  Asparagus  Rust  Control ;  and 
Bulletin  No.  175,  Tomato  Diseases  in  California.  Numerous  com- 
munications on  pear  blight  and  peach  blight  have  been  published  in 
the  horticultural  press. 

The  volume  of  work  which  has  been  demanded  of  the  Division  by 
legislative  and  private  sources  could  only  have  been  undertaken  with 
a  considerable  body  of  competent  assistants,  and  it  is  the  writer's  great 
pleasure  to  testify  to  the  efficiency  and  success  with  which  those  con- 
nected with  the  various  enterprises  have  responded  to  the  demands  upon 
them.  In  May,  1905,  Mr.  A.  M.  West  was  appointed  Assistant  Plant 
Pathologist,  and  began  work  at  Whittier  on  the  walnut  blight,  where 
he  has  since  been  located.  In  July  1,  1905,  Miss  E.  H.  Smith  received 
a  similar  appointment,  and  has  since  been  in  charge  of  the  laboratory 
and  office  work  at  Berkeley  during  the  writer's  frequent  absence. 
Numerous  temporary  assistants  have  been  employed  from  time  to 
time,  of  whom  several  have  since  received  more  permanent  appoint- 
ments. Mr.  B.  J.  Jones  began  work  on  the  pear  blight  in  March,  1905, 
and  has  practically  had  charge  of  the  field  work  during  the  past  year, 
still  continuing  in  this  capacity.  Mr.  E.  B.  Babcock  was  employed 
in  southern  California  in  the  lemon  rot  investigation  during  the 
summer  of  1905,  on  pear  blight  during  the  winter  of  1906,  and  again 
in  the  south  up  to  June,  1906,  when  he  retired  to  a  more  desirable 
position.  Mr.  R.  J.  McKeown  is  still  engaged  in  the  pear  blight  work, 
after  service  of  more  than  a  year.  Mr.  C.  O.  Smith  worked  on  lemon 
rot  during  the  summer  of  1905,  and  has  since  assisted  in  the  teaching  at 
the  University.  Mr.  H.  J.  Ramsey  was  stationed  at  Salinas  in  beginning 
the  beet  blight  work  in  1905,  and  has  since  been  employed  on  lemon 
rot,  p«ar  blight,  beet  blight  in  1906,  and  general  work  in  southern 
California,  being  now  stationed  at  Whittier.  Messrs.  T.  P.  Hunt  and 
N.  D.  Ingram  joined  the  pear  blight  force  in  September,  1905,  remain- 
ing on  that  work  through  the  campaign  of  the  season.  Mr.  Ingham 
has  since  taken  charge  of  the  University  Forestry  Substation  at  Santa 
Monica,  while  Mr.  Hunt  has  carried  on  the  beet  blight  work.  There 
have  also  been  employed  on  pear  blight  for  shorter  periods,  Messrs. 
W.  H.  Volck,  R.  Sale,  O.  Butler,  and  A.  B.  Mitzmain. 

PEAR  BLIGHT  WORK. 

The  work  of  greatest  magnitude  undertaken  has  been  that  in  the 
suppression  of  this  destructive  disease  of  pear  and  apple  trees  which 
has  recently  been  so  prevalent  in  this  State.  The  history  of  the  out- 
break  has   been   so   often   repeated   that   it   need   only   be   said   here 


UNIVERSITY   OF  CALIFORNIA EXPERIMENT  STATION. 

that  up  to  the  summer  of  190-4,  pear  blight,  except  for  a  few  scattering 
and  unautheriticated  reports,  was  unknown  in  central  and  northern 
California,  although  the  orchards  of  the  San  Joaquin  Valley  and  the 
southern  part  of  the  State  had  been  almost  wiped  out  several  years 
before.  In  the  Sacramento  Valley,  from  San  Joaquin  County  north, 
there  are.  or  were,  some  10,000  acres  of  the  finest  Bartlett  pear  orchards 
in  the  world.  In  addition  to  this  there  is  a  considerable  acreage  in 
Santa  Cruz,  Santa  Clara,  Alameda,  Sonoma,  Lake,  and  Napa  counties, 
while  numerous  apple  and  pear  orchards  of  greater  or  less  extent 
are  scattered  far  off  into  the  mountains  of  El  Dorado,  Placer,  Nevada, 
Sierra,  Plumas,  Lassen,  and  the  other  northern  mountain  counties. 

In  the  spring  of  1904  pear  blight  appeared  very  extensively  in  the 
Sacramento  Valley.  Much  alarm  was  felt  by  the  growers,  knowing 
the  history  and  result  of  the  disease  in  the  San  Joaquin,  and  the 
Experiment  Station,  the  various  County  Boards,  the  State  Com- 
mission of  Horticulture,  and  the  U.  S.  Department  of  Agricul- 
ture were  called  upon  for  advice  and  relief.  This  Division  being  new 
at  the  time,  consisting  of  the  writer  alone,  nothing  could  be  done  dur- 
ing the  summer  of  1904  except  to  determine  the  extent  of  the  outbreak 
by  much  traveling  about  through  the  whole  northern  region,  and  to 
assist  the  growers  as  much  as  possible  by  advice  as  to  the  nature  of  the 
disease  and  the  best  known  treatment,  and  by  inspecting  their  orchards. 
The  blight  developed  extensively  that  summer  and  invaded  most  of  the 
important  pear  districts.*  In  March,  1905,  appropriations  of  the  Legis- 
lature of  that  session  made  available  to  the  Station  about  $10,000  for 
the  "investigation"  of  pear  blight  during  the  succeeding  two  years. 
Meantime,  Professor  M.  B.  Waite,  the  leading  authority  on  pear 
blight,  had  been  sent  to  California  by  the  U.  S.  Department  of  Agri- 
culture, to  lend  all  possible  assistance  to  the  growers.  Considerable 
activity  was  also  being  displayed  by  the  State  and  various  County 
Boards  of  Horticulture  in  a  desire  to  do  what  was  possible  toward 
suppressing  this  disease. 

Recognizing  the  value  of  these  sources  of  assistance,  and  the  critical 
nature  of  the  situation,  it  seemed  best  to  the  Director  of  the  Station  and 
to  the  writer  in  using  the  State  appropriation,  to  combine  all  these 
efforts  in  an  endeavor  to  apply  as  quickly  and  as  generally  as  possible 
the  best  known  methods  of  pear  blight  control,  rather  than  to  start 
out  on  an  independent,  necessarily  extended  investigation  in  an  attempt 
to  develop  different  or  better  methods.  An  arrangement  was  accord- 
ingly made  whereby  the  Experiment  Station,  the  U.  S.  Department  of 
Agriculture,    and   the    State    Commission    of    Horticulture    agreed   to 

»  See  Report  of  California  State  Board  of  Horticulture,  1901-02;    Report  of  Com- 
onei  of  Horticulture,  1903-04;  and  Report  of  Thirty-first  Fruit  Growers'  Convention 
of  California  on  history  of  pear  blight  in  California. 


REPORT  OF  PLANT  PATHOLOGIST. 


223 


cooperate  as  fully  as  possible  in  the  work  of  suppressing  pear  blight 
in  the  State,  using  the  methods  recommended  by  Mr.  Waite.  It  should 
be  understood  that  our  own  part  in  this  work,  utilizing  the  State 
appropriation,  has  consisted  almost  entirely  in  an  effort  to  apply,  or 
to  encourage  the  application,  as  systematically  and  effectually  as 
possible,  of  the  method  of  treatment  outlined  by  the  Federal  expert. 
Nor  have  we,  save  for  minor  additions  or  variations  to  suit  local  con- 
ditions, anything  to  offer  different  from  the  fundamental  principles 


FTG. 


A  bad  case  of  pear  blight. 


of  the  nature  and  control  of  pear  blight  laid  down  by  Professor  Waite. 
It  is  but  fair  to  all  concerned,  however,  to  say  that  this  State  appro- 
priation is  being  expended  in  this  manner,  and  not,  as  with  our  other 
funds,  in  independent  investigation.  The  plan  and  method  of  work 
has  been  taken  from  Mr.  Waite 's  instructions  and  advice,  and  followed 
out  to  the  best  of  our  ability. 

The  general  idea  for  the  control  of  pear  blight  is  very  simple.  It 
consists  in  inspecting  the  trees  carefully  in  winter,  cutting  off  all  the 
affected  branches  below  the  point  to  which  the  disease  has  extended,  and 


224  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION. 

disinfecting  the  cut  surfaces  and  the  tools  with  an  antiseptic  solution. 
Trees  in  which  the  butt  is  affected  are  to  be  condemned  and  removed. 
The  method  also  insists  on  keeping  the  butt  and  main  limbs  of  the 
trees  free  from  all  sprouts  and  fruit  spurs,  recommends  a  certain  style 
of  pruning,  and  advises  as  much  moderation  as  possible  in  cultivation 
and  irrigation,  since  a  rapid  growth  of  the  tree  favors  the  disease. 
Cutting  out  the  blighted  twigs  as  they  appear  in  spring  and  summer 
is  recommended  with  some  reserve,  the  danger  being  that  at  this 
season  when  the  disease  is  active,  careless  cutting  or  disinfecting  may 
spread  rather  than  eradicate  the  blight.*  Particular  stress  is  laid 
upon  the  necessity  of  complete  eradication  of  the  blight  in  large 
districts,  rather  than  single  efforts  in  individual  orchards. 

To  accomplish  the  results  desired  in  California  it  seemed  necessary, 
(1st)  to  demonstrate  that  the  blight  could  be  successfully  controlled 
by  this  means;  (2d)  if  successful,  to  apply  the  method,  systematically 
and  thoroughly,  wherever  blight  was  present.  The  former  object  was 
attempted  and  fairly  well  accomplished  during  the  spring  of  1905, 
the  season  being  too  late,  when  the  appropriation  became  available, 
for  more  extended  work  at  that  time.  Professor  Waite,  accompanied 
by  the  writer  and  two  assistants  from  the  Experiment  Station,  Avent 
into  the  field  early  in  March  and  gave  demonstrations  in  the  Harkey 
orchard  near  Yuba  City,  in  Sntter  County,  and  at  the  Aloha  Fruit 
Company's  orchard  in  Anderson  Valley  in  Shasta  County.  One 
assistant  remained  at  each  place  to  continue  the  work.  The  Horticul- 
tural Commissioners  of  these  counties  cooperated  very  actively  in  the 
work,  and  aided  in  the  expense  of  keeping  men  in  their  sections. 
Sutter  County  also  continued  several  local  inspectors  on  the  work 
through  the  summer.  The  subsequent  results  in  both  these  cases 
seemed  to  warrant  the  continuance  of  the  work  on  a  larger  scale  during 
the  succeeding  season.  The  amount  of  blight  developing,  and  the 
damage  caused  by  it,  were  everywhere  in  direct  proportion  to  the 
work  done  during  the  winter  and  spring. 

Early  in  May  two  more  men  were  put  into  the  field  by  the  Station 
and  experiments  in  summer  cutting  were  carried  on  at  Vacaville,  in 
Solano  County,  and  considerable  information  obtained  as  to  the  best 
methods  of  handling  blight  in  California.  During  the  summer  the 
remaining  northern  counties  were  thoroughly  inspected,  the  number 
and  condition  of  the  pear  trees  ascertained,  and  the  locations  carefully 
mapped  preparatory  to  the  winter  campaign.  Considerable  was  also 
accomplished  in  instructing  the  growers  to  recognize  and  handle  the 
blight,  and  in  getting  into  touch  with  the  various  County  Boards  of 
Horticulture.     By  cooperation  with  the  State  Commission  of  Horticul- 

*  P  or  full  account  of  the  nature  and  control  of  pear  blight,  see  Report  of  Thirty-first 
Fruit  '  lonventiou  of  California  (1905),  p.  137. 


REPORT  OF  PLANT  PATHOLOGIST.  225 

ture  interest  was  aroused  in  some  counties  which  had  no  Board,  which 
resulted  in  the  appointment  of  such  a  body.  In  the  course  of  the 
summer  and  early  autumn  seven  field  assistants  were  trained  in  tne 
experimental  orchard  at  Vacaville.  This  was  done  by  a  month  or  more 
of  actual  work  at  cutting  out  blight  under  competent  instruction,  in 
order  that  they  might  become  familiar  with  every  type  of  infection 
and  all  phases  of  the  disease,  and  the  most  minute  details  of  control. 
These  men,  with  a  few  later  additions,  were  used  in  the  general  cam- 
paign of  the  winter  of  1905-06.  The  force  was  also  augmented  by  a 
number  of  men  from  the  U.  S.  Department  of  Agriculture. 

The  general  plan  of  work  adopted  during  the  past  winter  was  to 
locate  a  man  or  party  of  men  in  a  given  area  and  have  them  systemati- 
cally inspect  every  pear  and  apple  orchard,  tree  by  tree,  in  that  dis- 
trict. They  were  then  to  mark  the  trees  condemned  for  removal  on 
account  of  blight  in  the  butt,  instruct  the  owners  in  the  methods  of 
blight  eradication,  assist  in  training  their  help  for  the  work,  and 
finally  to  re-inspect  after  the  work  had  been  done.  It  was  not  the 
intention  to  have  the  Station  or  Department  men  do  any  considerable 
amount  of  actual  hand  labor.  The  district  to  be  covered,  as  originally 
planned,  included  the  counties  of  Contra  Costa,  Solano,  Yolo,  Sacra- 
mento, Placer,  Sutter,  Yuba,  Butte,  Tehama,  and  Shasta,  this  district 
seeming  to  be  most  in  need  of  the  work. 

Before  passing  to  the  details  of  the  work  actually  done  and  the 
results  accomplished,  it  may  be  said  in  general  that  it  was  found 
impossible  to  carry  on  operations  as  systematically  and  thoroughly  as 
could  be  desired.  This  was  due  mostly  to  the  inability,  disinclination, 
or  actual  refusal  of  some  growers  to  do  the  work  at  times  convenient 
to  our  limited  force  of  inspectors,  or  in  some  cases,  to  do  it  at  all.  To 
some  the  method  or  plan  of  work  failed  to  appeal ;  some  depreciated 
the  necessity  of  such  radical  procedure;  many  had  poor  help  or  none 
at  all;  some  failed  to  see  the  importance  of  doing  the  work  exactly 
according  to  instructions.  These  phases  of  the  problem  of  blight  con- 
trol will  be  considered  later  in  this  report.  Their  result  of  the  work 
of  the  past  winter  was  to  necessitate  much  duplication  of  inspection, 
a  great  deal  of  missionary  work  among  the  skeptical  or  dilatory  element, 
and,  in  order  to  secure  results  for  demonstration,  a  large  amount  of 
actual  hand  labor  by  the  inspectors  which  should  have  been  done  by 
the  growers.  These  features  of  the  work  were  instructive  in  showing 
what  can  or  can  not  be  counted  on  in  plans  for  the  future,  but  caused 
serious  delay  and  impairment  of  what  it  was  hoped  to  accomplish. 

In  practice  it  was  found  necessary  in  inspecting  trees  for  blight,  not 
simply  to  walk  through  the  orchard  looking  for  blighted  limbs  as  at 
first  seemed  sufficient,  but  each  inspector  had  to  be  provided  with  a 
gouge  or  chisel  and  make  a  thorough  examination  of  the  butt  and  trunk 


--0  UNTVERSTTX   OF  CALIFORNIA EXPERIMENT  STATION. 

of  every  tree,  in  order  to  detect  the  frequent  cases  of  hidden  blight  at 
that  point.  This  necessitated  further  the  condemning  of  many  appar- 
ently healthy  trees,  and  caused  much  delay,  or  refusal  on  the  part  of  the 
grower,  in  removing  them.  In  general,  however,  it  may  be  said,  that 
in  the  counties  named  practically  every  pear  and  apple  tree  was  care- 
fully inspected,  every  grower  was  seen  and  thoroughly  instructed  in  the 
method  of  work,  many  days  were  spent  by  the  men  in  every  important 
orchard,  a  large  amount  of  actual  hand  labor  was  performed  for  the 
sake  of  demonstration,  and,  in  addition  to  the  original  territory,  con- 
siderable more  was  covered  by  various  members  of  the  allied  forces. 

The  details  of  the  season's  work  may  be  taken  up  by  counties,  in 
order  to  show  what  has  been  done  in  each  section. 


SHASTA  COUNTY. 

Careful  attention  has  been  paid  to  this,  the  northernmost  county  of 
the  Sacramento  Valley,  on  account  of  its  important  pear  orchards  and 
the  fact  that  the  blight  had  only  a  slight  foothold  here  when  the  work 
started.  Our  work  has  been  greatly  assisted  by  the  cooperation  of 
Horticultural  Commissioners  Weaver,  Tharsing,  and  Lamiman,  of  this 
county.  Subsequent  to  the  preliminary  work  done  at  Anderson 
in  the  spring  of  1905,  the  orchards  of  the  county  have  been  inspected 
twice,  in  the  fall  of  1905  and  spring  of  1906,  and  a  strong  effort  made 
to  aid  the  growers  in  keeping  down  the  disease.  The  county  has  also 
been  visited  a  number  of  times  outside  of  the  regular  inspection.  •  About 
40.000  pear  trees  have  been  found  and  individually  inspected  in  this 
county.  The  removal  of  all  condemned  trees  has  been  vigorously  prose- 
cuted by  the  Commissioners,  and  almost  all  the  growers  have  shown  a 
disposition  to  carry  out  the  work  of  blight  eradication  in  the  best 
possible  manner. 

TEHAMA  COUNTY. 

Conditions  in  this  county  are  similar  to  those  in  the  last.     The  same 

inspections  have  been  made,  in  which  about  34,000  trees  were  found  and 

gone  over.    There  has  been  little  trouble  to  induce  most  of  the  growers 

to  carry  out  the  work  properly,  and  Commissioner  Coates  has  been 

vrery  active  in  his  official  capacity.     In  some  few  cases  the  work  has 

somewhat  neglected,  but  every  grower  has  had  ample  opportunity 

to  learn  proper  methods.     There  was  considerable  pear  bloom  in  parts 

of*  the  county  before  the  winter  work  was  completed,  which  resulted 

considerable  new  infection.     Conditions  in  general  are  better  than 

in  1905.     Apple  trees  everywhere  in  this  county,  as  indeed  all  over  the 

te,    contain    an    unusual    amount   of   infection   during  the   present 

summer. 


REPORT  OF  PLANT  PATHOLOGIST.  227 


BUTTE    COUNTY. 


The  pear  acreage  of  this  county  consists  mostly  of  a  number  of 
orchards  and  scattering  trees  about  Chico,  and  a  few  large  orchards 
in  the  southern  part  of  the  county.  The  blight  had  been  very  destruc- 
tive in  some  of  these  before  the  present  work  began,  and  serious  losses 
have  resulted.  Our  own  inspectors  have  spent  considerable  time  in  this 
territory,  but  the  work  there  has  been  mostly  in  charge  of  the  U.  S. 
Department  men.  The  pear  acreage  of  this  county  is  being  quite 
considerably  reduced  by  the  blight.  Horticultural  Commissioner  Stile 
has  given  active  cooperation  to  the  work  of  eradication. 

SUTTER  AND  YUBA  COUNTIES. 

A  considerable  amount  of  work  has  been  done  by  our  inspectors  in 
the  region  centering  about  Marysville,  and  the  results  obtained  there 
are  very  typical  of  what  may  be  expected  from  this  method  of  blight 
control.  The  trees  and  orchards  of  this  section  were  thoroughly 
inspected  in  the  fall  and  early  winter,  and  again  in  the  spring,  one  man 
spending  a  large  part  of  the  season  there.  The  various  growers  and 
their  workmen  were  carefully  instructed  in  the  methods  of  work,  and 
all  the  trees  inspected  individually  (as  in  every  case),  by  our  own 
expert.  He  was  very  generally  assisted  by  the  growers  and  some 
excellent  work  was  done,  various  individuals  demonstrating  their  ability 
to  handle  this  problem  alone.  Sutter  County  aided  materially  in  shar- 
ing the  expense  of  the  work,  Commissioners  Stabler  and  Kells  showing 
commendable  activity  in  endeavoring  to  promote  its  general  applica- 
tion. Commissioner  Harney  also  cooperated  on  the  Yuba  County  side. 
It  was  not  entirely  unfortunate  that  a  few  growers  near  Yuba  City 
refused  to  do  the  work  of  eradication  desired  of  them,  as  the  evident 
infection  radiating  from  these  orchards  after  the  blooming  season 
proved  an  excellent  object  lesson  to  the  community.  Surrounding 
orchards  received  a  profuse  blossom  infection,  spreading  some  distance 
in  all  directions. 

About  50,000  pear  trees  were  found  and  individually  inspected  in 
these  two  counties. 

PLACER  COUNTY. 

This  county  was  given  quite  a  thorough  preliminary  inspection  dur- 
ing the  summer  of  1905,  when  blight  was  not  yet  very  abundant,  not 
sufficient,  indeed,  to  arouse  any  great  public  interest  in  the  suppression 
of  the  disease.  When  inspected  again  during  the  winter  of  1906,  it 
was  found  that  a  great  increase  in  the  disease  had  taken  place.  Mr. 
Shear,  of  the  U.  S.  Department,  spent  considerable  time  in  the  county 


UNIVERSITY   OV  CALIFORNIA — EXPERIMENT  STATION. 

at  that  time,  but  neither  public  nor  individual  interest  in  blight  eradi- 
>n  has  become  general  enough  in  this  section  to  promise  very 
s  sfactory  results.  One  of  the  greatest  obstacles  is  the  large  number 
of  orchards  in  this  county  which  are  rented  to  Asiatics.  The  blight 
has  been  very  abundant  on  apples  in  the  county  during  the  present 
summer.  About  40.000  pear  trees  were  inspected  more  or  less  thor- 
oughly by  our  men. 

YOLO   COUNTY. 

The  district  about  Woodland  was  thoroughly  inspected  in  January, 
6,  and  the  Winters  region  has  been  given  considerable  attention. 
After  the  increase  in  the  U.  S.  Department  force,  this  county  was 
looked  after  by  one  of  their  men.  The  growers  have  been  thoroughly 
instructed  in  the  work,  and  are  in  most  cases  eager  to  apply  the  best 
'•  ds.  Conditions  in  this,  county  are  promising  as  regards  holding 
the  blight  in  check. 

SACRAMENTO  COUNTY. 

In  this,  our  largest  pear-growing  county,  a  great  and  fairly  success- 
ful effort  to  control  the  disease  has  been  made  both  by  the  growers 
and  those  in  charge  of  this  work.  The  County  Horticultural  Commission 
has  been  constantly  active,  since  the  first  serious  outbreak  of  blight. 
in  endeavoring  to  keep  down  the  disease,  and  it  is  largely  through  the 
personal  efforts  of  Commissioner  Cutter  that  the  pear  orchards  of  the 
great  river  section  are  in  as  good  condition  as  they  are  to-day,  judg- 
ing by  comparative  conditions  in  more  neglected  regions  which  have 
been  no  more  exposed  than  this.  Under  the  present  undertaking  a 
-iderable  number  of  men,  employed  variously  by  the  County,  Experi- 
ment Station,  and  U.  S.  Department,  have  done  a  large  amount  of 
work  in  this  section.  The  growers  have  almost  all  cooperated  fully, 
and  the  work  has  gone  forward  more  systematically  than  in  any  other 
large  district.  Operations  in  Sacramento  County  began  in  October, 
1905.  following  a  considerable  effort  on  the  part  of  the  county  horti- 
cultural officials  during  the  two  previous  summers.  The  work  has  been 
done  in  'Jose  cooperation  with  the  County  Board,  and  the  expense 
shared  by  it  to  a  considerable  extent.  The  late  Wm.  Johnston  and  his 
successor  on  the  Board,  Mr.  Greene,  both  residents  of  the  river  section, 
active  rind  of  great  assistance  in  the  local  operations. 

The  work  in  this  county  during  the  past  winter,  carried  on  by  two  of 
our  men  acting  as  county  inspectors,  two  other  Station  men,  and  two 
fro/o  the  U.  S.  Department,  resulted  in  the  inspection  of  208,300  trees 
'all  careful];,  examined  by  several  cuts  in  the  butt  with  a  gouge),  and 
in  addition  to  the  inspection  a  large  amount  of  the  actual  labor  of 
blight  removal   w;js  performed  by  the  inspectors.     Work  in  the  main 


REPORT  OF  PLANT  PATHOLOGIST.  229 

pear  district,  from  Rio  Vista  up  to  a  point  above  Courtland,  was  com- 
pleted during  the  winter,  but  some  of  the  scattering  sections  were  not 
reached.  There  are  over  250,000  pear  trees  in  the  county.  As  a  matter 
of  interest  as  representing  a  fairly  average  condition,  it  may  be  said 
that  in  the  river  district  the  208,300  trees  inspected  represented  110 
growers,  and  7,914  trees,  or  3.8  per  cent,  were  condemned  to  be 
destroyed.  Of  the  growers  affected,  at  least  100  removed  their  trees 
promptly  after  the  inspection,  and  only  one  of  the  remainder  made 
a  persistent  refusal.  It  can  scarcely  be  claimed,  however,  that  public 
sentiment  is  as  favorable  as  this  in  all  sections. 

Since  the  winter  work  ceased  the  county  has  kept  one  of  our  men 
in  the  field  all  summer,  and  most  of  the  growers  have  kept  up  a  con- 
stant effort  to  suppress  the  blight. 

SOLANO  COUNTY. 

The  work  in  this  county  has  been  very  similar  to  that  in  the  pre- 
ceding, and  it  has  occupied  a  major  portion  of  our  time  and  efforts, 
justly  so  on  account  of  the  large  pear  acreage  and  the  fact  that  the 
disease  has  been  more  virulent  here  than  in  any  other  section.  Two 
of  our  inspectors  received  their  salary  from  the  county  for  several 
months,  and  Commissioners  Blake,  Chadbourne,  and  Boyce,  particu- 
larly the  first  named,  have  been  most  active  in  assisting  the  work. 
Much  work  was  done  here  throughout  the  summer  of  1905  in  demon- 
strating eradication  methods  and  preparing  for  a  vigorous  winter 
campaign.  For  over  a  month  in  the  fall,  and  from  December  to 
March,  four  and  five  men  were  constantly  busy  in  Vaca  Valley, 
much  of  the  time  actually  cutting  out  blight  and  always  endeavoring 
to  spread  a  knowledge  of  the  methods  among  the  growers.  The  problem 
in  this  section  is  a  most  difficult  one,  owing  to  the  very  badly  affected 
condition  of  most  of  the  orchards,  and  the  disposition  of  the  growers 
to  take  an  indifferent  or  hopeless  attitude  as  to  the  possibility  of  con- 
trolling the  disease.  Conditions  are  worse,  and  we  have  done  more 
work  in  this  district  than  in  any  other.  For  the  sake  of  getting  any 
complete  demonstration  it  was  finally  necessary  to  select  a  certain 
natural  section  of  the  valley  for  the  work,  and  much  of  the  time  of 
our  inspectors  was  spent  in  doing  all  the  actual  work  of  blight  eradica- 
tion in  these  orchards  at  no  expense  to  the  owners.  A  few  growers, 
however,  assisted  in  the  latter  respect. 

The  demonstration  aimed  at  here  was  sufficient  to  justify  the  effort. 
Those  orchards  which  were  not  well  cleaned  or  were  left  untouched 
during  the  winter  received  an  unusual  amount  of  early  blossom  blight, 
while  those  in  the  section  well  worked  received  only  a  very  little  of 
this  from  these  neighbors.  This  carried  infection  over  into  the  late 
bloom  and  new  growth,  but  by  close  and  careful  summer  cutting  a 


UNIVERSITY   OF  CALIFORNIA EXPERIMENT  STATION. 

number  of  growers  have  succeeded  in  saving  their  crops  and  trees  at 
mparatively  trifling  expense.     Most  of  the  neglected  orchards  are 
I    s1  redemption. 

Two  men  were  stationed  at  Vacaville  through  the  spring  of  1906, 
following  up  the  development  and  spread  of  the  blight.  Altogether 
we  have  inspected  some  200,000  trees  in  this  county,  but  this  by  no 
means  represents  the  amount  of  work  done  on  account  of  the  large 
amount  of  labor  performed  by  the  inspectors,  and  the  experimental 
work  carried  on  in  this  district. 

Conditions  in  the  other  pear  sections  of  the  county,  the  Suisun  Val- 
ley, are  much  more  encouraging  than  at  Vacaville,  the  blight  having 
reached  here  a  year  later,  after  the  present  work  was  under  way. 

CONTRA  COSTA  COUNTY. 

There  are  about  75,000  pear  trees  in  this  county  and  they  have  as 
yet  been  only  slightly  affected  wuth  blight  in  a  few  orchards.  We  have 
inspected  the  county  twice  and  instructed  the  growers  in  the  methods 
of  work.  They  are  practically  unanimous  in  pushing  the  work.  Com- 
missioners Tevan  and  Sutton  have  cooperated  actively. 

LAKE  COUNTY. 

Blight  is  present  in  this  county  and  requires  attention.  Mr.  Swingle, 
of  the  U.  S.  Department,  spent  a  few  days  there  in  the  spring  of  1906, 
and  we  have  had  considerable  correspondence  with  various  growers,  but 
the  county  has  not  been  systematically  worked. 

EL   DORADO   AND   NEVADA   COUNTIES. 

These  counties  have  received  only  a  little  attention.  Blight  is 
present. 

SAN   LUIS   OBISPO   AND    MONTEREY    COUNTIES. 

These  counties  have  no  extensive  pear  orchards,  but  blight  is 
abundant  in  those  wmich  occur. 

SANTA   CRUZ  COUNTY. 

Blight  has  been  found  in  this  county  and  should  be  closely  wTatched, 
on  account  of  the  apple  industry. 

SAN  BENITO  COUNTY. 

Blight  has  been  found. 

ALAMEDA     AND    SANTA    CLARA    COUNTIES. 

I 

We  have  given   Hie  orchards  of  these  counties  considerable  inspec- 
and  found  no  cases  of  the  disease.     It  will  almost  certainly  enter 


REPORT  OF  PLANT  PATHOLOGIST.  231 

Santa  Clara  from  the  south  in  the  near  future,  and  should  be  care- 
fully watched  for. 

OTHER    COUNTIES. 

In  the  remainder  of  the  State  where  pears  are  grown  the  blight 
problem  is  not  pressing,  mostly  because  the  disease  has  already  ruined 
the  orchards.  Concerning  Napa  County  we  have  no  very  definite 
information,  but  the  disease  undoubtedly  exists  there. 

In  southern  California  the  blight  is  attracting  renewed  attention  on 
account  of  attacking  apple  trees  in  the  mountain  districts. 

GENERAL   CONCLUSIONS  REGARDING  PEAR  BLIGHT  ERADICATION   OR   CONTROL 

IN  CALIFORNIA. 

In  the  preceding  paragraphs  we  have  shown  what  has  been  done 
during  the  first  year  of  the  work,  under  the  plan  of  operation  adopted. 
It  is  but  reasonable  that  a  report  of  this  nature  should  indicate  some- 
thing as  to  the  prospects  and  plans  for  the  future. 

We  feel  satisfied  that  the  method  of  treatment  adopted  is  not  likely 
to  be  improved  upon,  save  perhaps  in  some  details.  We  have  followed 
out  some  lines  of  original  investigation  to  a  limited  extent,  and  hope 
to  push  them  further;  we  have  also  obtained  observations  of  value 
on  local  features  of  the  blight,  but  the  general  principles  laid  down 
still  hold.  The  pear-growers  of  California,  and  we  whose  province  it 
is  to  assist  them,  must  look  the  problem  in  the  face  and  make  the  most 
of  the  circumstances.  Avoiding  undue  enthusiasm  and  extravagant 
claims,  we  feel  justified  in  saying  that  in  our  experience  in  the  control 
of  pear  blight  since  1904  this  much  has  been  established: 

1.  That  thorough  work  in  winter  eradication  prevents  blossom-infec- 
tion in  spring. 

2.  That  the  larger  the  district  which  can  be  covered  in  winter  the 
less  will  be  the  infection  next  spring,  and  all  the  infection  will  come 
from  blight  which  remained  over  winter. 

3.  That  so  long  as  sources  of  infection  remain  over  winter,  producing 
infection  even  in  well-worked  orchards  near  by,  frequent,  prompt 
summer  cutting  and  removal  of  butt  sprouts  and  spurs  must  be 
practiced  in  order  to  prevent  serious  damage  and  loss  of  trees. 

4.  That  if  not  exposed  to  extremely  abundant  infection  from 
neglected  trees  near  by,  a  pear  orchard  can  be  profitably  maintained 
in  good  condition  and  cultivated,  pruned,  and  irrigated  in  the 
manner  necessary  to  secure  a  crop,  by  thorough  winter  blight  work 
and  prompt  summer  cutting  and  sprout  removal.  The  farther  away 
the  blight  can  be  held  the  less  will  be  the  trouble. 

The  general  application  of  the  work  requires,  with  all  growers 
education,  with  some  persuasion,  with   a  few  force.     Practically  the 


-"-  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 

greatest  difficulty  in  a  general,  systematic  clean-up  has  been  to  induce 
the  growers  to  do  the  work  with  any  degree  of  efficiency  and  sufficiently 
early  in  the  winter  so  that  our  inspectors  could  thoroughly  examine  the 
orchards  and  get  the  remaining  cases  out  before  the  new  season 
arrived.  It  is  often  difficult  to  get  help  to  do  the  work  properly,  or 
the  owner  does  not  realize  its  importance.  The  varying  quality  of 
human  nature  in  this  regard  can  only  be  partially  improved  by  exhorta- 
tion and  argument,  Few  actually  refuse  to  do  the  work,  but  many  slight 
or  postpone  it.  This  is  the  most  serious  difficulty  to  be  met.  Our 
horticultural  law  gives  the  County  Commissioners  power  to  force  the 
work,  and  in  a  few  counties  this  has  been  done  to  great  advantage, 
but  in  general  the  varying  status  of  the  Boards  in  different  counties, 
and  the  not  unnatural  disinclination  of  local  members  to  create 
trouble  with  their  neighbors,  render  hopeless  the  general  application 
of  the  law  under  present  conditions. 

It  appears  to  the  writer  that  the  desired  end  is  most  likely  to  be 
attained  by  stationing  permanent,  competent  inspectors  in  the  various 
pear-growing  centers  under  State  authority,  and  keeping  them  there 
the  year  round  to  aid,  instruct,  urge,  and  encourage  the  growers  in 
blight  eradication.  In  the  larger  districts  this  force  should  be  supple- 
mented at  county  expense.  Outside  aid,  such  as  that  from  the  U.  S. 
Department  of  Agriculture,  could  be  distributed  to  the  best  advantage 
in  the  State. 

"With  such  a  force  of  local  inspectors,  especially  if  given  authority 
to  enforce  blight  eradication,  conditions  should  be  so  adjusted  as  to 
assure  the  competency  of  these  men,  and  their  supervision  by  expert 
authority. 

It  is  hoped  to  adopt  this  method  as  far  as  possible  during  the  coming 
year,  stationing  the  men  available  more  permanently  and  with  less 
idea  of  covering  the  whole  territory  in  regular  order  than  was  the 
case  last  year.  This  will  afford  all  growers  who  desire  aid,  every 
opportunity  of  obtaining  it ;  but  in  large  districts  will  put  the  responsi- 
bility of  how  much  is  accomplished  toward  a  general  clean-up  more 
upon  the  growers  and  the  county. 

WALNUT  BLIGHT  INVESTIGATION. 

The  walnut  blight  is  a  very  serious  disease  of  the  English  walnut, 
which  occurs  all  over  California,  but  reaches  particular  importance 
in  the  southern  part  of  the  State  where  the  commercial  crop  is  princi- 
pally <_rrown.  Unlike  pear  blight  it  does  not  usually  affect  the  life 
or  vitality  of  the  tree  to  any  serious  extent,  but  exerts  its  harmful 
effect  on  the  amount  and  quantity  of  the  crop,  varying  from  year  to 
•  in  prevalence.  An  orchard  may  be  very  badly  affected  this  year, 
the  same  trees  produce  an  abundant  harvest  a  year  or  two  later. 


REPORT  OF  PLANT  PATHOLOGIST.  233 


# 


A  reduction  of  fifty  per  cent  or  more  in  this  valuable  crop  is  often 
occasioned  by  the  blight. 

The  disease  is  said  to  be  unknown  save  on  the  Pacific  Coast,  and 
has  been  previously  studied  only  by  Professor  Pierce,  of  the  U.  S. 
Department  of  Agriculture,  while  stationed  at  Santa  Ana,  Cal.  The 
latter  has  shown  the  blight  to  be  of  a  bacterial  nature,  caused  by  an 
organism  named  by  him  Pseudomona s  juglandis.  This  was  proved  by 
Professor  Pierce  to  be  the  active,  sole  cause  of  the  blight  by  isolation 
of  the  organism  from  diseased  tissues,  and  by  the  artificial  production 
of  the   disease   from   inoculations  with   the   germ   from   cultures.     A 


FIG.  2.    Bacterial  Blight  of  Walnuts. 

reduction  of  fifty  per  cent  in  the  occurrence  of  the  disease  has  been 
shown  by  this  investigator  as  a  result  of  spraying  twice  with  Bordeaux 
mixture,  after  first  removing  the  affected  twigs  from  the  tree.  The 
growers  as  a  whole,  however,  except  in  a  very  few  instances,  are 
attempting  no  treatment  for  the  blight  and  feel  deeply  concerned  at  its 
ravages.  The  disease  produces  black,  cankered  spots  on  the  young 
nuts,  causing  them  to  fall  prematurely  or  spoiling  the  kernel.  (Fig.  2.) 
Similar  spots  also  appear  on  the  youngest,  green,  new  shoots  (see 
Fig.  3),  but  these  heal  out  as  the  wood  hardens,  not  continuing  down 
the  twig.  In  bad  years,  however,  a  large  portion  of  the  terminal 
growth  (the  shoots  which  should  bear  the  crop  next  year)  is  killed 
in  this  way. 

2— bul  184 


FIG.  3.    Blighted  walnut  twigs. 


REPORT  OF  PLANT  PATHOLOGIST. 


235 


An  appropriation  was  made  by  the  last  Legislature  for  the  investi- 
gation of  this  disease,  which  fact  determined  the  first  work  to  be  taken 
up  by  the  Pathological  Laboratory  for  southern  California,  established 
at  the  same  time.  Temporary  quarters  were  obtained  through  the 
courtesy  of  the  Whittier  Board  of  Trade,  and  one  assistant  has  been 
constantly  employed  on  this  work  since  May,  1905.  The  writer  has 
also  given  much  personal  attention  to  this  investigation,  and  other 
help  has  been  added  from  time  to  time.  The  work  of  the  past  year 
has  consisted  in  a  bacteriological  study  of  the  organism  causing  the 
disease,    (Pierce's   determination  in   this   respect  being   substantiated 


3 


FIG.  4.    Spraying  for  Walnut  Blight  in  Spring  of  1906. 


by  our  results),  a  series  of  spraying  experiments  on  quite  an  extensive 
scale,  study  of  the  development,  spread,  etc.,  of  the  blight  in  the 
orchard,  and  general  study  of  the  walnut  and  its  culture.  We  will  not 
attempt  to  discuss  here  at  length  the  disease  or  details  of  the  investi- 
gation, which  still  continues.  Results  thus  far  have  shown  that  the 
trouble  is  a  peculiarly  difficult  one  to  control  for  a  number  of  reasons. 
The  results  of  our  spraying  experiments  do  not  appear  at  all  promising, 
though  this  will  be  continued  another  year.  Even  were  they  very 
favorable,  the  size  of  the  walnut  tree  makes  spraying  almost  prohibi- 
tive on  account  of  the  expense  and  difficulty.  An  immune  variety*  is 
very  feasible,  as  trees  vary  greatly  in  susceptibility  to  the  disease,  but 
this  will  not  help  the  existing  acreage.     Our  work  will  take  up  this 


2d6  ■  university  of  California— experiment  station. 

phase  oi  the  problem.  Careful  study  will  be  made  of  the  condition  of 
the  blight  organism  during  the  winter,  and  the  manner  of  the  first 
infection  in  spring,  hoping  in  this  way  to  obtain  some  suggestion  as  to 
a  preventive  treatment, 

LEMON  ROT  INVESTIGATION. 

This  work  was  undertaken  in  June,  1905,  at  the  request  of  the 
"Lemon  Men's  Club,"  of  Southern  California,  and  supported  in  part 
by  a  financial  contribution  from  the  same  source.     Since  the  establish- 


FIG.  5.    Brown  Rot  of  Lemons.    Untreated  Lemons.    (Decayed  fruit  in  boxes  at  left.) 

ment  of  the  temporary  laboratory  at  Whittier,  it  has  been  possible  to 
do  much  of  the  work  there  to  good  advantage,  in  connection  with 
observations  and  experiments  in  various  packing  houses  and  orchards. 
The  work  was  begun  at  the  Limoneira  Lemon  Company's  establishment 
at  Santa  Paula. 

The  trouble  in  question  i.s  a  peculiarly  virulent,  rapid-spreading  decay 
of  lemons  in  the  packing  house  and  marketing  box.  It  has  been  named 
the  "brown  rot"  by  the  growers,  in  distinction  to  the  ordinary  "blue 
mold"'  (PenicilUum)  rot.  The  growers  and  packers  knew  it  as  some- 
thing very  much  more  virulent  than  the  latter,  but  this  was  the  entire 
extent  of  information  as  to  the  nature  of  the  trouble,  and  means  of 
checking  it  were  entirely  lacking.    Losses  of  ten  per  cent  of  the  entire 


FIG.  8.    Beet  Blight. 


-+{)  UNIVERSITY   OF  CALIFORNIA EXPERIMENT  STATION. 

its  neighbors  very  rapidly  by  direct,  vegetative  growth  of  the  mold-like 
fungus  from  one  fruit  to  another  (Fig.  5),  but  no  spores  whatever  are 
formed  under  such  conditions  and  infection  can  only  take  place  by 
contact. 

Extensive  experiments  have  been  carried  on  in  disinfecting  the  wash- 
water  so  as  to  kill  the  fungus  without  injuring  the  fruit,  and  a  method 
worked  out  of  accomplishing  this  which  has  been  put  into  practice 
with  good  results  in  practically  every  lemon  house  in  the  State  (Fig.  6). 

It  has  also  been  found  possible  to  check  the  development  of  the  rot 
fungus  in  the  orchard  soil  by  simple  cultural  means,  and  this  is  being 
further  developed.  The  work  as  a  whole  is  in  very  satisfactory 
condition. 

BEET  BLIGHT  INVESTIGATION. 

The  blight,  or  "curly  top,"  of  the  sugar  beet  is  a  disease  which  has 
been  known  in  the  semi-arid  portions  of  this  country  for  a  number  of 
years,  and  caused  much  speculation  as  to  its  nature.  On  this  coast  the 
disease  has  been  the  cause  of  serious  losses  in  certain  seasons  for  some 
time,  and  the  growers  have  been  entirely  in  the  dark  as  to  the  nature 
or  handling  of  the  disease.  In  the  spring  of  1905  the  trouble  began  to 
appear  abundantly  in  certain  sections,  and  the  attention  of  the  writer 
was  called  to  the  need  of  information  concerning  this  disease  by 
Dr.  G.  W.  Shaw,  of  this  Station.  In  response  to  a  suggestion  made  to 
the  Spreckels  Sugar  Company  that  company  made  a  financial  guarantee 
to  the  Station  for  the  purpose  of  enabling  us  to  begin  a  study  of  the 
blight,  in  order  that  they  might  obtain  some  information  in  the  practi- 
cal handling  of  the  disease.  This  fund  was  subscribed  to  by  the  other 
beet  sugar  manufacturers  of  the  State. 

The  disease  in  question  is  a  peculiar  stunting  or  non-development  of 
the  plant,  occurring  often  under  conditions  apparently  very  favorable 
for  growth.  Some  years  in  large  areas  the  plants  stop  growing,  the 
leaves  curl  and  crinkle  in  a  peculiar  manner  (Fig.  7),  the  roots 
become  blackened  in  the  internal  rings  (Fig.  8),  and  soon  the  whole 
crop  is  a  complete  loss.  The  disease  has  been  studied  more  or  less  in 
different  places,  but  its  cause  has  never  been  discovered. 

An  assistant  was  stationed  at  Salinas  in  the  summer  of  1905,  working 
on  the  problem  there  in  connection  with  laboratory  studies  made  at  the 
University  at  Berkeley.  Observations  were  also  made  in  the  other  beet 
sections  of  the  State.  This  work  was  continued  so  long  as  conditions 
were  present  for  continuing  the  investigation,  and  commenced  again 
early  in  the  spring  of  1906,  and  is  still  continuing.  The  pathological 
and  field  work  has  been  in  charge  of  this  Division,  while  Professor  Shaw 
has  carried  on  a  series  of  moisture  determinations  and  investigation 
of  soil  conditions,  laying  out  a  series  of  plantings  for  this  purpose. 


REPORT  OF  PLANT  PATHOLOGIST.  241 

The  conclusion  reached,  and  substantiated  by  a  great  variety  of 
field  and  laboratory  investigations,  observations  and  experiments 
extending  over  two  seasons,  has  been  that  the  trouble  is  not  brought 
about  by  any  parasite  or  organism,  but  is  rather  due  to  a  derangement 
in  the  normal  functions  of  the  plant  which  can  not  be  fully  explained. 
The  disease  has  a  very  marked  relation  to  moisture  and  climate, 
especially  rainfall  at  certain  seasons,  but  presents  many  very  peculiar 
features.  It  is  a  very  definite  disease,  with  characteristic  symptoms, 
and  not  simply  the  injurious  effect  of  unfavorable  conditions.  The 
disease  is  one  of  a  number  of  so-called  "physiological"  plant  diseases, 
and  resembles  in  some  features  similar  diseases  of  the  tobacco,  China 
aster,  and  other  plants. 

Considerable  practical  benefit  seems  to  have  been  derived  from  the 
investigation  of  this  disease,  as  we  have  been  able  to  point  out  to  the 
growers  how  they  may  largely  avoid  the  trouble  by  planting  and 
cultural  practice  in  certain  relations  to  weather  conditions.  There  is 
reason  to  hope  that  in  the  future  the  trouble  can  be  almost  entirely 
avoided  by  this  means  unless  extremely  unusual  weather  conditions 
occur. 

It  is  hoped  to  continue  the  study  of  the  exact  nature  of  the  disease, 
as  a  better  understanding  of  this  wThole  class  of  plant  diseases  would 
be  of  great  practical  and  technical  interest. 

PEACH  BLIGHT  AND  "SHOT-HOLE  FUNGUS"  INVESTIGATION. 

The  serious  development  of  the  so-called  peach  blight  during  the  past 
two  seasons  has  rendered  it  imperative  for  us  to  seek  more  light  on  the 
nature  and  means  of  control  of  this  disease.  (Fig.  9.)  The  writer 
gave  the  matter  some  attention  during  the  season  of  1905,  and  in  the 
spring  of  1906  an  assistant  spent  considerable  time  in  the  field  in- 
vestigating conditions  in  regard  to  this  disease.  The  fungus  has  been 
studied  in  the  laboratories  at  Berkeley  and  Whittier,  and  arrangements 
made  for  quite  extensive  field  experiments  in  a  number  of  places  during 
the  coming  season.  Spraying  with  Bordeaux  mixture  in  December 
has  proved  so  effective  in  controlling  this  disease  that  wre  hope  to  make 
very  complete  demonstrations  during  the  season  of  1906-07.     (Fig.  10.) 

The  "shot-hole  fungus"  of  the  apricot,  caused  by  the  same  parasite 
(Coryneum),  is  the  cause  of  great  loss  in  this  crop,  and  it  has  been  our 
intention  to  include  this  also  in  the  same  investigation.  Experiments 
in  spraying  planned  for  1906  were  largely  a  failure  owing  to  excessive 
rains  at  the  proposed  time  for  spraying,  and  to  the  almost  total  failure 
of  the  crop  in  many  districts.  This  work  will  be  continued,  however, 
another  year  along  with  the  peach  work.  The  almond  is  also  badly 
affected  with  the  same  disease.  There  is  an  excellent  field  for  investiga- 
tion in  the  relation  of  the  Coryneum  fungus  to  the  various  stone  fruits. 


FIG.  9.    Peach  Blight  (Coryneum).    Unsprayed  tree. 


REPORT  OF  PLANT  PATHOLOGIST. 


237 


crop  before  shipment  were  experienced  in  many  instances,  besides  a 
large  amount  of  extra  handling  being  required,  and  frequent  excessive 
losses  in  shipment.  The  particularly  disastrous  feature  of  this  form  of 
decay  consisted  in  its  very  rapid  spread  through  the  boxes ;  one  affected 
lemon  soon  infecting  a  whole  box,  if  not  removed.  The  lemon  growers 
of  the  south  lost  upwards  of  $75,000  in  the  season  of  1904-05  from  this 
form  of  decay,  above  all  other  rot  and  shrinkage.  The  trouble  also 
occurs  in  the  orchard  to  some  extent  in  wet  weather. 

A  large  volume  of  work  has  been  done  in  this   investigation   by 


f  '  *#?$ 

ill   1 

■jfl 

fclffiii 


j£ 

mm 

/     ,       ;         i 

■■■~ 

—--' 

FIG.  6.    Brown  Rot  of  Lemons.    Wash-water  disinfected.    (One  decayed  lemon.) 


several  different  assistants,  and  the  problem  as  to  the  nature  and 
control  of  the  rot  seems  to  be  well  toward  satisfactory  solution.  The 
cause  of  the  trouble  was  soon  discovered,  and  found  to  be  a  fungus  not 
hitherto  described.  This  interesting  organism  has  been  named 
Pythiacystis  citrophthora  and  a  description  published  in  the  "Botani- 
cal Gazette."  The  investigation  has  revealed  something  entirely 
unsuspected  by  the  growers,  namely,  that  the  spores  of  this  fungus  are 
not  developed  upon  the  lemon  at  all,  but  entirely  in  the  soil  beneath 
the  trees  in  the  orchard.  Some  fruit  becomes  infected  in  wet  weather 
while  still  on  the  tree,  but  the  chief  source  of  infection  was  found  in 
the  water  of  the  washing  tank,  which  becomes  very  badly  infested  at 
times  with  spores  of  the  fungus  brought  in  with  the  dust  and  dirt  from 
the  orchard.    A  lemon  once  affected  and  stored  away  in  the  box,  infects 


FIG.  7.    Beet  Blight. 


FIG.  10.    Peach  Blight  (Coryneum).    Trees  sprayed  with  Bordeaux  mixture. 


244  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 


TOMATO  DISEASE  INVESTIGATION. 

Considerable  work  is  being  done,  particularly  in  southern  California, 
in  the  investigation  of  tomato  diseases.  Bulletin  No.  175  has  been  pub- 
lished on  the  subject  as  a  preliminary  report.  During  1906  a  disease 
not  mentioned  in  this  bulletin  has  proved  quite  serious;  this  is  the 
" Blossom-end  Rot,"  seemingly  an  active  bacterial  disease  as  occurring 
this  year.     (Fig.  11.)     The  summer  blight  or  wilt,  a  Fusarium  fungus 


FIG.  11.    Tomato  Fruit  Rot. 

disease,  is  our  most  serious  tomato  trouble  in  the  ordinary  course  of 
events,  and  stands  much  in  need  of  the  study  which  we  are  now  pre- 
pared to  give  it  at  the  Whittier  laboratory.  Spraying  demonstrations 
for  the  control  of  late  blight,  caused  by  the  potato  fungus  Phytophthora, 
will  also  be  carried  on  in  the  same  section  which  is  a  center  of  tomato 
growing. 

ASPARAGUS  RUST. 

This  work,  the  earliest  undertaking  of  this  Division  in  the  State, 
is  still  receiving  some  attention.  The  results  of  the  treatment  recom- 
mended as  a  result  of  the  investigation  were  particularly  good  in  1905. 
preventing  the  rust  entirely  in  large  fields  when  the  disease  was 
abundant  on  all  sides.  Work  with  resistant  varieties  and  in  applying 
the  method  of  treatment  to  various  conditions  is  still  continuing. 

ROSE  DISEASES. 

This  subject  has  been  made  the  subject  of  some  study  and  experiment, 
and  material  obtained  for  a  bulletin  on  the  subject.  A  very  common 
and  destructive  disease  has  been  found  in  the  State  which  has  never  been 
previously  reported,  the  nature  of  other  troubles  determined,  and  a 
method  of*  treatment  developed  which  has  features  of  superiority  over 
any  present,  practice. 


REPORT  OF  PLANT  PATHOLOGIST.  245 


CITRUS  DISEASE  INVESTIGATION. 

With  the  founding  of  the  laboratory  for  southern  California,  oppor- 
tunity is  afforded  for  what  has  long  been  a  pressing  need  in  that  section, 
a  general  investigation  of  citrus  diseases.  Particularly  the  so-called 
"Gum  Disease"  requires  much  careful  study.  This  work  is  now  being 
entered  upon  and  will  be  prosecuted  vigorously. 

OTHER  INVESTIGATIONS,  PRESENT  AND  FUTURE. 

The  above  includes  the  principal  lines  of  work  engaged  in  up  to  July, 
1906.  Many  other  matters,  however,  are  constantly  receiving  attention 
in  the  laboratory  and  field,  amounting  in  the  aggregate  to  nearly  as 
much  as  the  special  investigations.  Some  of  these  subjects  are  greatly 
in  need  of  more  special  consideration,  and  will  no  doubt  receive  it  soon 
with  our  increased  facilities.  The  root  rot  or  "Oak  Fungus"  disease 
of  various  fruits,  the  apple  mildew  and  scab,  the  melon  wilt,  onion 
mildew,  and  a  number  of  others  may  be  included  in  this  class.  All 
these  and  others  are  frequent  subjects  of  inquiry  to  which  we  can  give 
no  satisfactory  answers.  Too  much,  however,  must  not  be  undertaken 
at  once  or  the  work  allowed  to  become  superficial,  as  is  the  tendency 
under  such  conditions  as  ours.  What  is  needed  is  accurate,  thorough 
investigation,  the  accomplishments  and  results  of  which  can  not  be 
measured  or  predetermined  by  time,  resources  or  anything  but  the 
quality  of  the  work  itself  and  the  nature  of  the  problem.  One  under- 
taking may  result  in  a  brilliant  success  almost  immediately,  and  another 
give  no  practical  results  whatever  after  long-continued  effort  made  with 
equal  or  superior  ability. 

The  preparation  of  the  present  report  has  been. largely  contributed 
to  by  several  of  my  assistants,  particularly  Messrs.  B.  J.  Jones,  A.  M. 
West,  H.  J.  Ramsey,  T.  F.  Hunt,  E.  B.  Babcock,  and  Miss  E.  H.  Smith. 


:46  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 


PLANT  DISEASES  OF  CALIFORNIA. 


The  following  list,  Avhile  not  compiled  with  the  idea  of  absolute  com- 
pleteness, may  be  of  some  value  in  indicating  the  ordinary  plant 
diseases  of  the  State,  and  the  comparative  occurrence  of  some  which 
are  most  important  in  other  parts  of  the  country.  The  list  will  also 
serve  as  a  basis  for  a  more  complete  synopsis,  to  be  added  to  from  time 
to  time.  No  distinction  is  made  as  to  the  cause  of  disease,  fungus  or 
otherwise,  the  writer  wishing  to  lessen  the  tendency  to  make  plant 
pathology  synonymous  with  the  study  of  parasitic  fungi. 

POME  FRUITS. 

APPLE. 

Powdery  Mildew  (Podosphaera  oxyacanthae). — This  is  one  of  the 
most  serious  apple  troubles  in  the  State.  The  new  growth  is  attacked, 
with  a  stunting  effect  in  spring,  and  the  blossoms  considerably  injured. 
The  disease  occurs  all  over  the  State,  particularly  in  the  mountain  and 
coast  regions. 

Scab  (Venturia  inaequalis).—  Apple  scab  has  only  recently  become 
general  in  the  State,  appearing  first  in  the  mountain  regions.  It  is 
more  prevalent  than  ever  before  during  the  present  season. 

Blight  (Bacillus  amylovorus). — The  disease,  more  commonly  called 
pear  blight,  has  attacked  apples  with  unusual  virulence  during  1906. 
This  is  particularly  the  case  in  the  mountain  regions,  both  north  and 
south. 

Root- Rot  and  "Toadstool"  or  "Oak  Fungus"  Disease. — This  trouble 
is  severe  on  apples  in  the  northern  mountain  districts.  At  least  two 
distinct  diseases  may  be  recognized,  one  a  decay  of  the  roots  and  lower 
trunk,  caused  by  perhaps  more  than  one  species  of  toadstool  fungus 
coming  from  the  soil.  There  is  apparently  some  ground  for  the  popular 
idea  that  this  disease  occurs  more  frequently  on  ground  where  oak 
trees  formerly  stood.  The  native  oaks  are  frequently  attacked  in  a 
similar  manner.  The  second  form  of  disease  appears  to  come  about 
through  infection  at  wounds  or  pruning  scars  on  the  trunk,  the  fungus 
running  down  into  the  heart  of  the  limbs  and  trunk  and  thence  into 
the  cambium  and  bark.  From  recent  observations  we  are  led  to 
believe  that  the  little  toadstool  fungus,  SchizophyJlum  commune,  is  the 
cause  of  this  trouble. 


REPORT  OF  PLANT  PATHOLOGIST.  247 

"Baldwin  Spot." — This,  or  a  similar  trouble,  marked  by  the  appear- 
ance of  sunken,  discolored  spots  on  the  surface  of  the  fruit,  is  common 
on  a  number  of  varieties  of  apple,  and  of  serious  importance.  The 
cause  is  not  known. 

Grown  Gall. — This  trouble  gives  much  trouble  in  nurseries,  but 
apparently  does  not  result  as  seriously  in  the  orchard  tree  as  with  the 
similar  disease  on  stone  fruits. 

Canker,  Rots,  etc.— The  various  diseases  of  this  sort  which  are 
prevalent  in  many  parts  of  the  country,  either  do  not  occur  or  are  not 
conspicuous  in  California. 

PEAR. 

Scab  (Venturia  pirina). — This  has  been  the  greatest  obstacle  to  pear 
production  in  the  State,  causing  immense  losses  in  quality  and  quantity 
in  many  seasons.  The  disease  is  of  comparatively  recent  occurrence 
in  many  sections,  but  is  now  practically  universal.  Preventive  spray- 
ing is  not  always  successful,  owing  to  prevalence  of  rain  at  the  proper 
season.    The  trouble  was  extremely  abundant  in  1906. 

Blight  (Bacillus  amylovorus). — This  disease  now  invades  all  except 
a  very  small  section  of  the  State,  and  menaces  the  pear  industry.  Great 
efforts  are  being  made  for  its  suppression. 

Leaf  Blight  (Entomosporinm). — This  disease  has  not  been  observed 
in  the  State. 

Crown  Gall. — Quite  uncommon  on  pears. 

LOQUAT. 

Blight  (Bacillus  amylovorus). — Pear  blight  affects  the  loquat  quite 
seriously  in  some  instances. 

QUINCE. 

Blight  (Bacillus  amylovorus). — Quinces  are  also  affected  by  this 
disease  when  considerably  exposed  to  infection. 

STONE  FRUITS. 

Owing  to  the  various  combinations  as  to  root  made  in  propagating 
these  trees,  as  well  as  their  close  relationship,  the  various  species  may 
be  considered  collectively  as  regards  the  diseases  to  which  they  are 
subject. 

ALMOND,  APRICOT,  CHERRY,  PEACH,  PLUM,  PRUNE. 

Crown  Gall.— Common  and  injurious  on  all  the  stone  fruits,  both  in 
orchard  and  nursery. 

Root  Rot  ("Toadstool"). — Serious  in  many  sections,  causing  trees 
to  die  in  gradually  enlarging  areas  in  the  orchard.  Apparently  caused 
by  more  than  one  species  of  toadstool. 

Root  Knot  (Nematode). — Occurs  sometimes  in  nurseries  on  these  and 
other  plants,  but  not  general  and  not  an  orchard  pest. 


248  UNIVERSITY  OF  CALIFORNIA— EXPERIMENT  STATION. 

Brown  Rot  (Monilia). — This  is  not  yet  a  serious  pest  in  California, 
and  is  greatly  held  in  check  by  the  rainless  summer  season.  During 
the  past  two  seasons  of  late  spring  rains,  however,  the  rot  has  been 
quite  abundant  and  destructive  on  apricots,  some  plums,  and  early 
peaches,  especially  near  the  coast.  Monilia  was  probably  more  preva- 
lent in  the  State  in  the  spring  of  1906  than  ever  before,  and  in  general 
seems  to  be  gradually  gaining  in  prevalence.  Considerable  damage  to 
the  young  twigs  of  apricots  occurred  from  this  cause  during  the  past 
spring.    Cherries  are  not  affected,  so  far  as  the  writer  has  observed. 

Leaf  Curl  (Exoascus  deformans). — This  disease  is  extremely  preva- 
lent in  the  State  on  peaches  almost  every  year,  but  is  readily  controlled 
by  proper  spraying. 

A  similar  disease  on  plum  has  been  observed,  but  the  peach  is  com- 
monly the  only  fruit  affected  in  this  manner. 

Mildew  (Podosphaera  oxyacanthae). — This  is  seen  rather  commonly 
on  peach,  but  can  hardly  be  called  a  serious  pest. 

Blight:  Shot-hole  Fungus  (Coryneum). — This  trouble  has  been 
extremely  severe  on  peaches  throughout  most  of  the  State  in  1905  and 
1906.  The  fruiting  wood  becomes  badly  infected,  causing  gumming 
and  the  death  of  the  buds.  Apricots  are  attacked  by  apparently  the 
same  fungus,  but  with  a  somewhat  different  effect,  a  scabbing  of  the 
fruit  being  the  most  conspicuous  symptom.  Many  of  the  buds  are  killed 
as  on  peaches,  but  the  gumming  of  the  twigs  is  much  less  pronounced. 
The  scabby  effect  is  seen  to  some  extent  on  the  fruit  of  the  peach,  when 
the  disease  is  very  prevalent.  On  the  almond  the  leaves  are  most 
affected,  showing  a  shot-hole  effect  and  dropping  from  the  tree. 
Apricot  leaves  also  become  perforated,  but  do  not  fall. 

Cherries,  plums,  and  prunes  are  not  so  commonly  affected. 

Other  shot-hole  fungi  than  the  Coryneum  occur  in  the  State,  but 
have  not  been  conspicuous  in  recent  years. 

Rust  (Puccinia  pruni). — The  prune  rust  is  abundant  in  California, 
but  rarely  becomes  a  pest  save  in  the  drier,  southern  portions.  In  most 
sections  where  sufficient  water  is  available  throughout  the  summer,  the 
rust  appears  only  in  fall,  on  the  leaves  which  are  about  to  fall  from 
natural  maturity.  In  dry  regions,  however,  where  the  trees  suffer  for 
water,  the  rust  sometimes  appears  quite  early  and  causes  the  foliage 
to  fall.     Peaches,  plums,  prunes,  and  occasionally  almonds  are  affected. 

Sour  Sap. — Under  this  name  is  popularly  known  a  common  and 
serious  trouble  with  stone  fruits.  The  disease  is  characterized  by  the 
sudden  death  of  a  tree  or  branch  in  full  leaf,  commonly  in  the  early 
spring.  It  is  not  a  gradual  sickening  or  dying,  as  may  occur  under  any 
avorable  conditions,  but  a  sudden  withering  of  a  healthy,  vigorous 
tree.  Apricots  and  prunes  are  most  commonly  affected,  sometimes  other 
fruits.     There  is  no  evidence  of  any  parasite  or  organism  in  con- 


REPORT  OF  PLANT  PATHOLOGIST.  249 

nection  with  the  disease,  but  it  appears  rather  to  be  brought  about  by 
certain  weather  conditions,  typically  a  period  of  cold,  wet  weather  fol- 
lowing an  unseasonably  warm  period  in  early  spring.  Apparently  a 
very  vigorous  activity  is  started  in  the  tree  and  then  suddenly  checked, 
resulting  in  a  stagnation  and  subsequent  fermentation  of  the  sap. 
Primarily  the  trouble  is  purely  functional  from  all  appearances. 

Die  Back,  and  Dying  in  Spots. — These  general  terms  include  many 
cases  of  troubles  with  stone  fruits  in  which  the  trees  gradually  die  from 
the  top  from  no  cause  above  ground.  Hardpan,  alkali,  changes  in  water 
level,  dry  soil,  and  various  other  unfavorable  conditions  are  responsible 
for  cases  which  are  not  due  to  crown  gall,  root  rot,  or  insect  or  gopher 
attacks.  The  "dying  in  spots"  referred  to  is  seen  in  many  prune, 
peach,  apricot,  almond,  and  cherry  orchards,  where  the  trees  in  certain 
areas  survive  only  up  to  a  certain  age,  then  gradually  dying  back  from 
the  top.    The  cause  is  usually  one  of  the  above  named. 

Split  Pit. — This  disease  is  seen  principally  in  peaches,  and  shows  itself 
.as  a  cracking  and  shattering  of  the  pit  of  the  mature  fruit,  commencing, 
however,  when  the  peach  is  very  young.  The  characteristic  effect  is 
more  than  simply  a  separation  of  the  two  halves  of  the  pit,  showing  as 
a  cracking  of  the  whole  stone  into  small  fragments.  A  gumming,  which 
breaks  out  on  the  surface  of  the  fruit,  usually  accompanies  the  trouble. 
The  cause  appears  to  be  physiological  rather  than  the  effect  of  any 
parasitic  organism. 

Seasonal  Effects. — One  of  the  most  common  of  troubles  with  fruit 
trees  in  the  State  is  that  produced  by  the  vagaries  of  our  mildly  uncer- 
tain climate.  Particularly  in  the  coast  regions  of  southern  California 
do  the  peaches  and  their  relatives,  as  also  the  apples  and  walnuts,  lose 
complete  reckoning  of  the  season  and  suffer  accordingly.  Trees  bloom- 
ing in  fall,  remaining  bare  until  July  or  August,  bearing  two  crops  of 
fruit  a  year  and  showing  other  evidences  of  confusion  is  the  result. 
This  has  a  disastrous  effect,  resulting  usually  in  a  dying  back  to  the 
main  fork  or  larger  limbs.  Several  uniform  seasons  following  this  may 
enable  the  tree  to  form  a  new  top  again.  A  great  many  orchards,  par- 
ticularly of  peach,  apple  and  hard-shelled  walnuts  were  killed  or  badly 
injured  in  this  way  in  the  season  of  1903-04 :  in  1904-05  they  became 
still  more  affected,  but  in  1905-06  normal  conditions  more  nearly  pre- 
vailed. Different  varieties  of  fruit  are  variously  affected;  the 
"Saucer"  or  Peento  peach  being  notably  unaffected. 

Of  stone  fruit  diseases  of  serious  importance  in  other  parts  of  the 
country,  the  Peach  Yellows,  Little  Peach,  and  Rosette,  the  Peach  Scab 
(Cladosporium)  Black  Knot  (Plowrightia)  of  the  plum  and  cherry,  and 
the  Plum  Pockets  (Exoascus)  are  not  known  to  the  writer  to  occur  in 
California. 

3— bul  184 


250  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 

SMALL  FRUITS. 

Diseases  of  the  small  fruits  are  not  abundant  in  California,  but  a  few 
may  be  mentioned. 

BLACKBERRY. 

Rust  (Gymnoconia  interstitalis) . — Blackberry  rust  is  common  in  the 
State  and  conspicuous  by  the  powdery  mass  of  bright  orange-colored 
spores  which  it  produces  on  the  lower  side  of  the  leaves. 

CURRANT. 

Mildew  (Sphaerotheca  mors-uvaet) . — This  powdery  mildew  attacks 
currants  quite  commonly. 

DEWBERRY,    LOGANBERRY. 

Leaf  Spot. — These  fruits  are  considerably  attacked  by  a  fungous  leaf 
spot. 

Fruit  Rot  (Botrytis  cinerea) . — The  common  Botrytis  mold  caused 
considerable  decay  of  ripe  berries  during  the  past  season. 

STRAWBERRY. 

Leaf  Spot  (Sphaerella).— This  disease,  causing  numerous  purple 
dead  spots  on  the  leaves,  is  rather  common. 

SUBTROPICAL  FRUITS. 

ORANGE,  LEMON,  POMELO. 

The  diseases  of  citrus  fruits  in  California  have  heretofore  received 
but  little  attention.  The  common  troubles  may  be  named,  but  in  several 
cases  this  is  the  extent  of  existing  information. 

Blue  Mold  (Penicillium) . — This  is  the  common  form  of  citrus 
decay.  Examination  shows  that  twro  species  of  Penicillium  are  present 
and  about  equally  abundant :  P.  glaucum,  the  blue-green  form,  and 
P.  digit atum,  the  olive-green.  The  species  are  quite  distinct,  both 
biologically  and  morphologically.  Powell's  recent  work  on  citrus 
decay  in  transportation  has  shown  that  there  is  little  or  no  infection 
from  these  molds  save  in  bruised  fruit. 

Broun  Rot  (Pythiacystis  citrophtliora,  n.  sp.). — This  form  of  decay, 
which  is  principally  confined  to  lemons,  has  been  recently  investigated 
by  this  Division,  as  indicated  elsewhere.    It  has  been  extremely  virulent. 

Gum  Disease  ^Fig.  12). — This  is  the  only  common  citrus  tree  disease 
irj  the  State.  It  occasions  large  losses  in  lemons,  and  some  in  oranges. 
The-  disease  manifests  itself  in  exudations  of  gum  from  the  trunk. 
commonly  stopping  abruptly  at  the  crown.  The  gum  breaks  out 
through  the  bark,  the  cambium  and  inner  bark  become  disorganized,  and 


REPORT   OF  PLANT   PATHOLOGIST. 


251 


in  severe  cases  the  tree  dies.  Other  less  severe  cases  recover,  or  are 
helped  by  cleaning  out  the  affected  bark  and  painting  over  the  wound 
with  an  antiseptic.  The  disease  is  not  primarily  a  root  rot,  and  the 
root,  in  most  cases,  does  not  become  affected.  The  trouble  occurs  in 
trees  in  poorly  drained  situations  or  otherwise  under  unfavorable  con- 


FIG.  12.    Gurn  Disease  of  Citrus  Trees. 


ditions.  So  far  as  our  observations  have  shown  it  is  a  purely  functional 
disorder  and  not  produced  at  all  by  any  parasitic  organism. 

A  somewhat  different  form  of  gum  disease  also  occurs,  in  which 
the  breaking  out  of  the  gum  occurs  from  the  limbs  of  the  tree,  rather 
than  from  the  main  trunk  near  the  ground. 

Die  Back.— Various  forms  of  citrus  disease  characterized  by  this 
general  term  occur  in  California,  but  there  is  no  trouble  of  this  sort 


-■"'-  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION. 

of  a  very  definite  nature.  "Die  back"  is  not  a  common,  characteristic, 
or  serious  trouble    in    the    State..     There  is  particularly  no  fungous 

-  ase  of  this  sort  which  is  at  all  common. 

Puffy  Orange. — This  is  a  trouble  which  affects  particularly  the 
Washington  Navel  in  certain  seasons,  exhibiting  itself  as  a  "puffiness," 
or   wrinkling,   expansion,   and  sponginess   of  the   skin.      The   interior 

somes  structureless  and  insipid.  The  trouble  is  physiological  and 
produced  by  an  abnormal  development  from  some  cause  not  well 
understood. 

OLIVE. 

Tuberculosis  (Bacillus  oleae). — This  bacterial  disease  of  the  olive 
has  previously  occasioned  considerable  alarm  in  the  State,  but  experience 
has  proved  it  to  be  not  a  very  serious  or  destructive  trouble.  The 
disease  is  fairly  abundant,  particularly  in  the  Sacramento  Valley,  but 
is  not  the  cause  of  any  severe  commercial  damage. 

VEGETABLES  AND  FIELD  CROPS. 

ASPARAGUS. 

Bust  (Puccinia  asparagi).— Asparagus  rust  continues  to  prevail  in 
the  State  and  has  been  the  cause  of  very  severe  losses  in  this  crop. 
The  disease  has  been  fully  as  severe  as  ever  during  the  past  season.  The 
treatment  recommended  by  this  Station  has  proven  successful  in  many 
instances  where  properly  carried  out,  but  a  large  acreage  of  the  crop 
is  rapidly  succumbing  to  the  disease. 

BEAN. 

Anthracnose  (Colletotrichum  lindemuthiamim) . — This  disease,  which 
produces  a  spotting  or  rusting  of  the  pods  of  string  beans,  can  not  be 
called  a  serious  pest  in  California.  It  is  much  less  abundant  than  in 
most  parts  of  the  country. 

Bust  (Uromyces  appendiculatus) . — The  true  red  rust  of  the  bean 
occurs  sometimes  on  bush  beans  and  causes  more  or  less  damage.  It  was 
quite  abundant  in  1906. 

Powdery  Mildew  (Erysiphe  poly goni)  .  —  This  disease  is  not  uncom- 
mon on  bush  beans  and  occasionally  causes  damage. 

The  white  lima,  our  principal  bean  crop  and  one  of  the  large 
industries  of  California,  is  notable  for  its  freedom  from  fungus  diseases 
and  injurious  pests  of  every  sort. 

BEET. 

Blight  or  Curly  Top.— This  serious  sugar-beet  disease  occurs  very 
destructively  in  the  State  during  certain  seasons.  Its  development  was 
rather  limited  in  1906.    The  disease,  from  considerable  investigation  by 


REPORT  OF  PLANT  PATHOLOGIST.  253 

this  Station,  appears  to  be  of  a  physiological  rather  than  a  parasitic 
nature,  brought  about  by  climatic  and  other  natural  conditions. 

Leaf  Spot  (Cercospora  beticola) .—The  leaf  spot  of  the  beet  is  not 
serious  or  destructive  in  this  State.  On  the  sugar  beet  it  is  practically 
or  wholly  unknown. 

Root  Rot.— A  root  rot  of  sugar  beet  seedlings  occurs  quite  largely  in 
wet  weather.  Affected  plants  usually  recover,  but  produce  a  branched 
and  misshapen  root  as  a  result  of  the  injury  to  the  original  tap  root. 
The  trouble  appears  to  be  due  to  a  form  of  Rhizoctonia. 

Rust  (Uromyces  betae).  —  This  disease  is  found  quite  commonly  on 
the  leaves  of  table  beets  which  are  left  in  the  ground  over  winter.  It  is 
not  at  all  serious. 

Nematode  Worm  {Heterodera  radicicola)  .  —  This  serious  trouble  of 
sugar  beets  in  Germany  has  been  observed  in  California,  but  has  not 
thus  far  occurred  in  serious  abundance. 

CABBAGE,  TURNIP,   RADISH. 

Club  Foot  (Plasmodiophora  brassicae) . — This  trouble,  which  pro- 
duces large  swellings  or  tumors  on  the  roots  of  these  plants,  occurs  in 
this  State  but  is  not  at  all  common. 

White  Rust  {Cystopus  candidus) .—This  fungus  is  common  in  the 
State  on  the  shepherd's  purse,  an  allied  plant  of  the  cabbage  family. 

Black  Rot  {Pseudomonas  campestris) . — This  bacterial  disease  of 
the  cabbage  and  similar  plants  is  not  known  to  the  writer  to  occur  in 
California. 

CELERY. 

Leaf  Blight  (Septoria  petroselini)  .  —  This  disease  occurs  to  a  con- 
siderable extent  in  the  large  celery  districts  of  the  State. 

CUCUMBER. 

The  out-of-door  crop  of  cucumbers  in  the  State  is  not  seriously 
affected  by  any  disease.  As  grown  to  a  limited  extent  in  greenhouses, 
the  following  troubles  occur : 

Powdery  Mildew  {Erysiphe  polygoni) . — This  is  not  uncommon,  but 
of  no  serious  importance. 

Nematode  Worm  {Heterodera  radicicola)  .  —  The  root-knot  trouble 
caused  by  these  pests  has  been  seen  in  the  case  of  one  greenhouse  in  the 
State. 

Stem  Rot  (Sclerotinia  libertiana) . — This  disease,  causing  a  rotting  of 
the  stem  at  the  surface  of  the  ground,  has  been  seen  in  one  instance. 

MELON. 

Wilt,  Stem  Rot  (Fusarium) . — Both  cantaloupes  and  watermelons  are 
seriously  affected  in  this  State  by  a  wilting  and  dying  of  the  plant, 
caused  by  a  species  of  Fusarium. 

4— bul  184 


254  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 


ONION. 


Downy  Mildew  {Peronospora  schleidiana) . — In  the  great  onion  seed 
farms  of  the  State  this  disease  is  frequently  the  cause  of  severe  loss 
during  the  wet  winter  months. 


PEA. 

Powdery  Mildew  (Erysiphe  polygoni). — The  pea  mildew  is  common 
and  more  or  less  troublesome  on  crops  grown  in  the  rainy  season. 

POTATO. 

Blight  (Phytophthora  infestans). — Potato  blight  occurs  in  the  State 
in  more  or  less  abundance  in  the  foggy  coast  districts  and  during  the 
rainy  season.  In  general  the  main  potato  crop  of  the  State  is  entirely 
free  from  this  disease. 

Rhizoctonia  Disease. — This  is  common  in  the  State,  but  of  very  little 
serious  importance. 

Scab  (Oospora  scabies). — Potato  scab  is  common  in  California,  but  a 
less  serious  pest  than  in  many  other  sections. 

Stem  Rot,  Dry  Rot  (Fusarium). — This  disease,  showing  as  a  wilting 
and  dying  of  the  potato  plants  and  blackening  and  dry  rot  of  the  tubers, 
is  our  most  serious  potato  trouble.  It  is  not,  however,  abundant  in 
the  most  important  potato  sections,  but  appears  to  develop  most  freely 
in  the  foothill  and  mountainous  regions,  where  the  crop  is  grown  in  a 
limited  manner. 

SQUASH,   PUMPKIN. 

Bacterial  Wilt. — These  plants,  particularly  the  squash,  are  affected 
very  commonly  with  a  serious  bacterial  wilt,  causing  the  death  of  the 
vines.  The  writer  has  not  satisfied  himself  that  this  is  the  same  disease 
as  the  Eastern  one  of  similar  plants,  caused  by  Bacillus  tracheiphilus, 
inasmuch  as  the  symptoms  of  the  disease  are  somewhat  different,  and 
cucumbers  are  apparently  unaffected  by  the  trouble  which  occurs  here. 

Powdery  Mildew  {Erysiphe  sp.). — This  is  common  on  squash  leaves 
but  of  no  particular  importance. 

SWEET   POTATO. 

Wilt  {Fusarium) . — A  wilting  and  dying  of  sweet  potato  vines,  caused 
by  a  species  of  Fusarium,  is  the  frequent  cause  of  large  losses  in  this 
crop  in  the  Merced  district.  The  use  of  new  seed  from  outside  districts 
has  proven  very  satisfactory  in  avoiding  the  trouble. 

TOMATO. 

Will,,  Blight  (Fusarium). — This  is  our  most  serious  tomato  disease. 
It  was  Jess  abundant  than  usual  in  1906. 


REPORT  OF  PLANT  PATHOLOGIST.  255 

Winter  Blight  (Phytophthora  infestans). — This  common  fungus  of 
the  potato  occasionally  attacks  winter  tomatoes  very  seriously  during 
the  rainy  season. 

Fruit  Rot,  Blossom  End  Rot. — During  1906  a  disease  of  this  sort  was 
very  abundant  all  over  the  State.  The  cause  appeared  at  first  to  be 
undoubtedly  bacterial,  but  further  investigation  left  considerable  doubt 
as  to  the  nature  of  the  disease. 


GRAINS  AND  FORAGE  CROPS. 

ALFALFA. 

Rust  ( Uromyces  sp. ) . — A  true  rust  of  alfalfa  is  considerably  trouble- 
some in  the  southern  portions  of  the  State  during  the  spring  season. 
The  disease  invariably  disappears  in  the  cuttings  after  the  rains  have 
ceased. 

Leaf  Spot  (Pseudopeziza  medicaginis) . — This  common  alfalfa  disease 
is  not  rare  in  the  State,  but  in  general  can  not  be  called  a  serious  trouble. 

GRAINS. 

Smut  and  rust  are  extremely  common  and  destructive  in  all  our 
grains,  of  which  wheat  and  barley  are  most  important. 


NUT,  FOREST  AND  SHADE  TREES. 

almonds.     (See  stone  fruits.) 

POPLAR. 

Leaf  Spot  (Marsonia  populi). — This  disease,  causing  black  spots  on 
the  leaves  and  twigs  and  defoliation  of  the  trees,  was  very  abundant 
in  the  State  in  1906. 

SYCAMORE. 

Blight  (Gloesporium  nervisequum) . — This  disease  is  extremely  abun- 
dant, in  fact  universal,  on  the  sycamore  trees  of  the  State  every  spring. 

WALNUT. 

Bacteriosis  (Pseudomonas  juglandis). — This  very  serious  trouble  of 
the  English  walnut  causes  great  losses  in  the  crop  every  year.  The 
disease  was  very  abundant  in  1906. 

Die  Back. — Most  of  the  older  hard-shell  orchards  of  southern  Cali- 
fornia are  dead  or  nearly  so,  and  rapidly  being  removed  on  account  of 
the  dying  back  of  the  branches  to  the  main  trunk.  The  cause  appears 
to  lie  in  the  occurrence  of  several  unseasonably  warm  winters  in  recent 
years. 


256  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION. 

FLORAL  AND  ORNAMENTAL. 

CHINA  ASTER. 

Yellows. — This  physiological  disease  of  the  aster  is  of  quite  common 
occurrence  in  California. 

CARNATION. 

The  carnation  rust  (Uromyces  caryophyllinus) ,  wilt  (Fusarium  sp.) , 
and  leaf  spot  (Septoria  dianthi),  all  occur  in  California,  but  are  not 
generally  troublesome  or  destructive.  The  two  last  mentioned  have 
been  known  to  cause  severe  losses  in  the  propagation  of  cuttings. 

CHRYSANTHEMUM. 

Fust  {Puccinia  chrysanthemi) . — The  chrysanthemum  rust  is  well 
distributed  and  common  over  the  State,  yet  can  not  be  considered  a 
serious  obstacle  to  the  growing  of  this  plant.  In  the  majority  of  cases 
it  is  only  plants  suffering  for  water  or  growing  in  very  dry  ground 
which  become  seriously  affected. 

DAHLIA. 

Powdery  Mildew. — A  mildew  is  common  on  dahlias,  but  no  serious 
injury  has  been  observed  from  this  source. 

HOLLYHOCK. 

Fust  (Puccinia  malvacearum) . — The  hollyhock  rust  is  common  in 
the  State  on  hollyhocks  and  wild  mallow. 

OLEANDER. 

Tuberculosis. — A  bacterial  disease  similar  to  that  of  the  olive,  and 
caused  by  the  same  organism,  has  been  found  on  oleanders.  It  is  not 
at  all  general  or  serious. 

ROSE. 

Powdery  Mildew  (Sphaerotheca  pannosa  and  8 ph.  humuli) . — Two 
different  species  are  found  in  the  rose  mildew  so  common  in  the  State. 
The  former  of  the  above-named  attacks  the  hybrid  roses,  Crimson 
Rambler,  etc.,  producing  a  thick  mat  of  felty  mycelium  on  the  shoots 
and  twigs.  In  this  the  perithicial  spore  stage  is  found  embedded. 
This  species  is  very  common  in  the  State.  Sphaerotheca  humuli  attacks 
the  tea  roses,  producing  a  more  delicate  mycelium  upon  the  leaves,  and 
developing  only  conidial  spores.     This  is  also  extremely  abundant. 

Rust  ( Phragmidium  subcorticium) . — The  rose  rust  is  very  common 
oil  the  hybrid  roses. 

Cane  BUght. — A  die  back  or  blight  of  rose  canes,  caused  by  an  appar- 
ently undescribed  fungus,  is  abundant  in  California  and  causes  serious 
damage. 


STATION     PUBLICATIONS.  257 


STATION  PUBLICATIONS  AVAILABLE  FOR  DISTRIBUTION. 


REPORTS. 


1896.  Report    of    the    Viticultural    Work    during    the    seasons    1887-93,    with    data 

regarding  the  Vintages  of  1894-95. 

1897.  Resistant    Vines,    their    Selection,    Adaptation,    and    Grafting.      Appendix    to 

Viticultural  Report  for  1896. 

1898.  Partial   Report  of   Work  of  Agricultural   Experiment   Station   for   the  years 

1895-96   and    1896-97. 
1900.     Report  of  the  Agricultural  Experiment  Station  for  the  year  1897-98. 

1902.  Report  of  the  Agricultural  Experiment  Station  for  1898-1901. 

1903.  Report  of  the  Agricultural  Experiment  Station  for  1901-1903. 

1904.  Twenty-second  Report  of  the  Agricultural  Experiment  Station  for  1903-1904. 


TECHNICAL   BULLETINS— ENTOMOLOGICAL  SERIES. 


Vol.   1,  No.  1.     Wing  Veins  of  Insects. 

No.  2.     Catalogue  of  the  Ephydridae. 


BULLETINS. 


Reprint.  Endurance  of  Drought  in  Soils  of  the  Arid  Region. 

No.  128.  Nature,  Value  and  Utilization  of  Alkali  Lands,  and  Tolerance  of  Alkali. 
(Revised  and  Reprint,  1905.) 

133.  Tolerance  of  Alkali  by  Various  Cultures. 

140.  Lands  of  the  Colorado  Delta  in  Salton  Basin,  and  Supplement. 

141.  Deciduous  Fruits  at  Paso  Robles. 

142.  Grasshoppers  in  California. 
144.  The  Peach-Worm. 

147.  Culture  Work  of  the  Substations. 

148.  Resistant  Vines  and  their  Hybrids. 

149.  California    Sugar   Industry. 

150.  The  Value  of  Oak  Leaves  for  Forage. 

151.  Arsenical   Insecticides. 

152.  Fumigation  Dosage. 

153.  Spraying    with    Distillates. 

154.  Sulfur  Sprays  for  Red  Spider. 
156.  Fowl  Cholera. 

158.  California  Olive  Oil ;   its  Manufacture. 

159.  Contribution  to  the  Study  of  Fermentation. 

160.  The  Hop  Aphis. 

161.  Tuberculosis   in   Fowls.      (Reprint.) 

162.  Commercial  Fertilizers.      (Dec.  1,  1904.) 

163.  Pear   Scab. 

164.  Poultry  Feeding  and  Proprietary  Foods.     (Reprint.) 

165.  Asparagus  and  Asparagus  Rust  in  California. 

166.  Spraying  for  Scale  Insects. 

167.  Manufacture  of  Dry  Wines  in  Hot  Countries. 

168.  Observations  on  Some  Vine  Diseases  in  Sonoma  County. 

169.  Tolerance  of  the  Sugar  Beet  for  Alkali. 

170.  Studies  in  Grasshopper  Control. 

171.  Commercial  Fertilizers.      (June  30,  1905.) 

172.  Further  Experience  in  Asparagus  Rust  Control. 

173.  Commercial   Fertilizers.      (December,   1905.) 

174.  A   New   Wine-Cooling  Machine. 

175.  Tomato  Diseases  in  California. 

176.  Sugar  Beets  in  the  San  Joaquin  Valley. 

177.  A  New  Method  of  Making  Dry  Red  Wine. 

178.  Mosquito  Control. 

179.  Commercial   Fertilizers.      (June,    1906.) 

180.  Resistant  Vineyards. 

181.  The   Selection  of   Seed-Wheat. 

182.  Analyses  of  Paris  Green  and  Lead  Arsenate.       Proposed  Insecticide  Law. 

183.  The  California  Tussock-moth. 


258 


UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION. 


CIRCULARS. 


No.   1. 


4. 
5. 
i . 
9 

10. 

11. 

12. 
13. 
15. 

16. 

17. 


Texas    Fever. 

Blackleg. 

Hog  Cholera. 

Anthrax. 

Contagious  Abortion  in  Cows. 

Remedies    for    Insects. 

Asparagus   Rust. 

Reading   Course   in   Economic 

Entomology.      (Revision.) 
Fumigation    Practice. 
Silk  Culture. 

The  Culture  of  the   Sugar  Beet. 
Recent   Problems  in  Agriculture. 

What  a  University  Farm  is  For. 
Notes  on   Seed- Wheat. 
Why     Agriculture     Should    be 

Taught  in  the  Public  Schools. 


No.  18. 
19. 
20. 
21. 

22. 

23. 
24. 
25. 

26. 

27. 


Caterpillars    on    Oaks. 

Disinfection  of  Stables. 

Reading    Course    in    Irrigation. 

The  Advancement  of  Agri- 
cultural  Education. 

Defecation  of  Must  for  White 
Wine. 

Pure  Yeast  in  Wineries. 

Olive    Pickling. 

Suggestions  Regarding  Exam- 
ination   of   Lands. 

Selection  and  Preparation  oi 
Vine    Cuttings. 

Marly  Subsoils  and  the  Chlo- 
rosis or  Yellowing  of  Citrus 
Trees. 


Copies  may  oe  had  on  application  to  Director  of  Experiment  Station,  Berkeley,  Gal. 


